The present disclosure relates to a turbocharger.
The turbine housing in the turbocharger disclosed in Japanese Laid-Open Patent Publication No. 2017-082762 is provided with an accommodation space that accommodates a turbine wheel. This accommodation space is connected to a scroll passage, which draws exhaust gas from the outside of the turbine housing to the accommodation space. The accommodation space is also connected to a connection passage, which discharges exhaust gas from the accommodation space. The connection passage extends along the rotation axis of the turbine wheel. A section of the connection passage on the downstream side in the exhaust flow direction is connected to a merging passage, which discharges exhaust gas from the inside of the turbine housing. In addition, the turbine housing has a bypass passage extending from the scroll passage to the merging passage while bypassing the accommodation space.
The turbocharger of the above publication includes a wastegate, which has a pivot shaft pivotally supported by the turbine housing. A first valve member is fixed to the pivot shaft of the wastegate. Also, a second valve member is fixed to the pivot shaft of the wastegate to be separated from the first valve member in the circumferential direction about the pivot axis of the pivot shaft. When the pivot shaft pivots to one side, the first valve member closes the outlet portion of the connection passage. When the pivot shaft pivots to the other side, the second valve member closes the outlet portion of the bypass passage.
The turbine housing of the turbocharger disclosed of the above publication has a first sealing surface at the outlet portion of the connection passage. The first sealing surface is inclined with respect to a plane orthogonal to the central axis of the outlet portion of the connection passage to face the outlet portion of the bypass passage.
In the turbocharger disclosed in the above publication, the angle by which the first sealing surface is inclined with respect to the second sealing surface, which faces the second valve member at the outlet portion of the bypass passage, is smaller than that in a case in which the first sealing surface is orthogonal to the central axis of the outlet portion of the connection passage. This reduces the pivoting range of the wastegate from the state in which the first valve member of the wastegate is in contact with the first sealing surface to the state in which the second valve member is in contact with the second sealing surface.
In the turbocharger of the above publication, the first sealing surface is inclined as if cut obliquely. Therefore, the opening area of the outlet portion of the connection passage is larger than that in other cases. Accordingly, in the turbocharger of the above publication, the first valve member of the wastegate is relatively large in order to close the outlet portion of the connection passage. Therefore, the turbocharger of the above publication has room for further improvement in terms of miniaturization of the wastegate.